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Whoops, started this thread accidently in res hvac........Now let's put it where it belongs.

The facts as I know them minus a couple

Box temp 43
r404 system
evap split 2 degrees
41 degree temp exiting evap
38 degree suction line temp at compressor
suction = 80+/-
high side 250
ambient = 85
Cose suction and system takes approx 3 minutes to pull down to 0 psig. Lock down high and leaks back to 20 psig in about 2 min. Changed one condensor motor. Evap and condensor both clean. Dang thing acts like overcharge but nothing been added. Been running for 4 years till this. System is a Bohn with the beacon system attached. Small box (8x10), w/15 ft of line. Overnite, will not go below 39.

Any thoughts? I got pulled off for some A/C while boss went to look at this one after I had started. He's baffled, but as a result I don't have info on subcool and condensor splitt, etc

Is compressor running constantly? Superheat readings are taken directly off of beacon board located in box on front of evap.. Superheat should be running 8-10 deg. Instructions for board are inside cover. This board is somewhat self diagnostic and may be flashing an error code(probably a bad sensor). Make sure if you replace sensor(s) you use the latest version from beacon. These sensors are prone to water intrusion and failure. These units are tricky to diagnose if your not familar with them, as they try to refrigerate even when they sense a problem, rather than shutting down w/total loss of refrigeration.

This thing has an eletronic expansion valve on it as per the Bohn website. Stepper motor regulates superheat based on superheat sensor mounted on suction line and inputting to logic control. Are definetly getting some refreration effect as when you raise box temp to say 50 degrees, you will get a small split. Unit will cool (excruciatingly slowly). Boss walked into it this morn and it was 37 degrees after working all night. That's the setpoint and unit still would not pump down and cycle off. No solenoid valve on this systm. When box gets down to temp, stepper motor shuts off refrigerant supply through EV. Gotta be the electronic expansion valve stuck and not moving or weak compressor will not move refrigerant throught the system and pump down when through. I'm leaning towards the latter as the compressor takes approx. 2 min just to pull accumulator to 0 Psig.